anticholinestearses pptx it acts by inihibiting anticholieneastearse

it acts by inihibiting the anticholieneastrese

1. ANTICHOLINESTERASES ( PHARMACOKINECTICS AND THERAPEUTICS USES ) Dr Harshit Tiwari Junior resident -1 Department of Pharmacology and Therapeutics KING GEORGE MEDICAL UNIVERSITY LUCKNOW

2. PHARMACOKINECTICS Physostigmine 1.It is rapidly absorbed from g.i.t. and parenteral sites. 2. In the eyes, it penetrates cornea freely. 3. It crosses blood-brain barrier 4.Disposed after hydrolysis by ChE.(cholinesterase)

3. Neostigmine 1. These are poorly absorbed orally; oral dose is 20–30 times higher than parenteral dose. 2. They do not effectively penetrate cornea or cross blood-brain barrier. 3. They are partially hydrolysed and partially excreted unchanged in urine.

4. Pyridostigmine Resembles neostigmine in all respects but is dose to dose less potent longer acting, less frequent dosing is required in myasthenia gravis. Edrophonium Resembles neostigmine in action, has a brief duration (10–30 min), I t is suitable only as a diagnostic agent for myasthenia gravis.

5. Organophosphates These are absorbed from all sites including intact skin and lungs. They are hydrolysed as well as oxidised in the body They are little is excreted unchanged in urine Echothiophate It is an organophosphate with quaternary structure. It is water soluble; and was used as a long acting miotic.

6. Tacrine It is a lipophilic acridine compound It interacts with ChE in a manner analogous to edrophonium. It crosses blood-brain barrier and has a longer duration of action. Donepezil 1.Another centrally acting anti- AChE .2.It is long-acting and suitable for once daily administration

7. Rivastigmine This lipophilic relatively cerebroselective ChE ( cholineastrase ) inhibitor It has been introduced for Alzheimer’s disease (AD) , Galantamine This natural alkaloid inhibitor of cerebral AChE has in addition weak agonistic action on nicotinic receptors. It is being used to afford symptomatic relief in AD

8. THERAPEUTICS USES As MIOTIC a) In Glaucoma – Physostigmine (0.1%) is used only to supplement pilocarpine. Miotics are now 3rd choice Drugs, used only as add on therapy advanced case (b) To reverse the effect of mydriatics after refraction testin g (c) To prevent formation of adhesions between iris and lens or iris and cornea, and break them which are formed due to iritis and corneal ulcer

9. 2. Myasthenia gravis (a) . Treatment is usually started with neostigmine 15 mg orally 6 hourly; (b) . Pyridostigmine is an alternative which needs less frequent dosing. (c) . Diagnostic tests for myasthenia gravis : Initially edrophonium 2 mg is injected i.v. as a test dose. If nothing happens then the remaining 8 mg is injected after 30–60 sec. edrophonium test — improvement → myasthenic crisis Inject edrophonium (2 mg. i.v. ) no improvement or worsening → cholinergic crisis

10. 3. Postoperative paralytic ileus/urinary retention This may be relieved by 0.5–1 mg s.c. Neostigmine 4. Postoperative decurarization Neostigmine 0.5–2.0 mg (30–50 μ g /kg) i.v. , preceded by atropine or glycopyrrolate 10 μ g /kg to block muscarinic effects 5. Cobra bite . the primary treatment, neostigmine + atropine prevent respiratory paralysis.

11. 6. Belladonna poisoning Physostigmine 0.5–2 mg i.v. repeated as required is the specific antidote for poisoning with belladonna 7. Other drug overdosages Tricyclic antidepressants, phenothiazines and many antihistaminicshave additional anticholinergic property. Overdose symptoms and coma produced by these drugs are partly antagonized by physostigmine.

12. 8. Alzheimer’s disease The relatively cerebroselective anti-ChEs , rivastigmine, donepezil and galantamine are now commonly used These above augment cholinergic transmission

13. References Tripathi, K. D. (2018)  Essentials of medical pharmacology . 8th ed. New Delhi, India: Jaypee Brothers Medical. Goodman, L., Gilman, A., Brunton, L., Lazo , J. and Parker, K., (2006).  Goodman & Gilman's the pharmacological basis of therapeutics . New York: McGraw-Hill.

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